Adjustable woven fabric



y 4, 1968 H. M. HELLAND 3,383,278

ADJUSTABLE WOVEN FABRIC Fil'ed Sept. 27, 1967 3 Sheets-Sheet l y 1968 H. M. HELLAND ADJUSTABLE WOVEN FABRIC 3 Sheets-Sheet 2;

Filed Sept. 27, 1967 May 14, 1968 H. M. HELLAND ADJUSTABLE WOVEN FABRIC 3 Sheets-Sheet 5 Filed Sept. 27, 1967 INVENTOR jfi g vg fiej/azd m azzarmys United States Patent 3,383,278 ADJUSTABLE WOVEN FABRIC Howard M. Helland, Appleton, Wis., assignor to Appleton Mills, Appleton, Wis., a corporation of Wisconsin Continuation-impart of application Ser. No. 631,381,

Apr. 17, 1967. This application Sept. 27, 1967, Ser.

Claims. (Cl. 162-411) ABSTRACT OF THE DISCLOSURE An endless fabric, such as a papermakers felt, composed of a series of generally parallel warp yarns and having cross machine yarns or fibers located at an acute angle up to 80 with respect to a line normal tothe Warp yarns. The cross machine fibers are freely ad ustable with respect to the warp yarns and by ad usting the angularity of the cross fibers, when the felt is on the paperrnaking machine, the porosity and drainage rate of the felt as well as the finish characteristics of the paper being made, can be varied, thereby extending the useful life of the fabric.

This application is a continuation-in-part of application Ser. No. 631,381, filed Apr. 17, 1967 .and entitled Adjustable Woven Fabric, now .abandoned.

In a papermaking machine, the papermakers felt is utilized to pick up or receive a freshly laid web of wet paper after it leaves the forming wire and conduct the paper web through the pressing operation where additional water is removed from the wet paper web. For effective operation, the highest possible rate of water drainage through the felt and the requisite surface smoothness of the paper being made must be provided and sustained over the longest possible period of time in order to produce the maximum useful felt life. Further, the papermakers felt must have a high degree of dimensional stability, and the physical properties of the felt must be uniform throughout its dimension so that the paper is uniform in quality and finish.

The present invention is directed to an improved papermakers felt in which the cross machine yarns or fiber-s :are located at an acute angle with respect to the warp or longitudinal yarns and can be adjusted to angularity when the felt is on the papermaking machine to vary its drainage rate and the finish characteristics of the paper. More specifically, the paperrnakers felt of the invention includes a series of generally parallel warp yarns which are disposed longitudinally of the direction of travel of the felt. The cross machine fibers, in the form of yarn, cross machine-oriented fibers, or a combination of yarn and fibers, are positioned at an acute angle up to 80 with respect to a line norm-a1 to the warp yarns. The felt may be initially woven with the cross yarns or fibers at an angle of 90 with respect to the warp yarns. The woven felt is then cocked or skewed to adjust the angu- 1 larity of the cross yarns or fibers and subsequently stabilized in the skewed position. After installation, the angularity of the cross yarns or fibers can be adjusted from the original skewed position to vary the drainage characteristics of the felt and nature of the finish of the paper.

The papermakers felt of the invention has distinct advantages in drainage, service life and finish characteristics of the paper over conventional paper-in akers felts. By adjusting the angularity of the cross yarns or fibers with respect to the warp yarns when the felt is on the papermaking machine, the relative size of the openings or passageways between the yarns can be altered to thereby vary the permeability and drainage characteristics of the felt, as desired.

The adjustability of the cross yarns or fibers provides that the machine operator can adjust the felt structure to compensate for the gradual closing up of the felt due to the accumulation of fines and other contaminants from the paper finish in the woven structure as well as structural compaction due to the continuous application of pressure. Also, because the functional properties of a felt are important only to that portion of the felt which is being operated on at the nip of the paper machine press, the adjustable feature and the skewed configuration of the cross-machine yarns or fibers makes it possible to open up the felt structure by enlarging the openings for reconditioning and cleaning during the time that the felt is outside of the nip.

The adjustability of the cross yarns or fibers can also serve to vary the finish characteristics of the paper. A variety of paper grades are often required to 'be made during the time a felt is in position on the machine. The conventional felt cannot operate in an optimum fashion for all of the various grades, and the papermaker generally comprises, as for example, by reducing machine speed to provide more time for expressed water to pass through the felt, or by accepting a paper finish level that is less than that desired for a given paper grade.

The present invention, however, provides a degree of adjustment, enabling a more nearly optimum felt-paper grade relationship to be obtained. This is accomplished by adjusting the cross yarns or fibers with respect to the warp yarns when the felt is on the machine to thereby correspondingly alter the drainage characteristics of the felt and the finish characteristics of the paper and enable a variety of paper grades to be produced with the same felt.

Conversely, for a single grade of paper, the adjustability of the cross yarns or fibers also aids in maintaining a uniform drainage rate. During use, the openings in the felt will tend to become clogged with fines and other contaminants, and the openness may decrease due to structural compaction of the felt. By progressively enlarging the openings by adjustment of the angularity of the cross yarn-s or fibers, the effective openness of the felt can be maintained so that the drainage rate will be uniform throughout the life of service of the felt.

Other objects and advantages will appear in the course of the following description.

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a diagrammatic plan view of a portion of a papermakers felt as woven, and before cocking;

FIG. 2 is a view similar to FIG. 1 showing the yarns after cocking;

FIG. 3 is a diagrammatic side elevation of a typical press section of a paperm-aking machine employing a felt of the invention and having a provision for adjusting the angularity of the cross yarns while the felt is on the machine;

FIG. 4 is 'a plan view showing a portion of the felt of of FIG. 3 as supported on the adjustable roller of the papermaking machine with the cross yarns positioned at an angle of about 45 with respect to a line normal to the warp yarns;

FIG. 5 is an enlarged plan view showing the yarn orientation of the felt of FIG. 4;

FIG. 6 is a view similar to FIG. 4 showing the cross yarns adjusted to an angle of about 0 with respect to a line normal to the warp yarns;

FIG. 7 is an enlarged plan view showing the yarn orientation of the felt of FIG. 6',

FIG. 8 is a view similar to FIG. 4 showing the cross yarns adjusted to an angle of about 60 with respect to a line normal to the warp yarns;

FIG. 9 is an enlarged plan view showing the yarn orientation of the felt of FIG. 8;

FIG. 10 is a view similar to FIG. 4, showing the cross yarns adjusted to an angle of about 45 with respect to a line normal to the warp yarns and at an angle of about 90 with respect to the position of the cross yarns of FIG. 4;

FIG. 11 is an enlarged plan view showing the yarn orientation of FIG. 10;

FIG. 12 is a diagrammatic plan view of a portion of a papermakers felt with the angular disposition of the cross fibers indicated by the line B; and

FIG. 13 is 'a view similar to FIG. 12 and showing a portion of the width of the felt being cocked.

FIG. 1 illustrates a woven fabric which is particularly adaptable for use as a papermakers felt. The fabric or felt 1 comprises a series of generally parallel warp yarns or strands 2, and cross yarns 3 are interwoven with the warp yarns 2 and are freely adjustable in angularity with respect to the warp yarns.

The yarns 2 and 3 can be formed of any fibrous, monofilament, or multifilament material. For example, the yarns 2 and 3 may be composed of animal fibers such as wool, vegetable fibers such as cotton, mineral fibers such as glass, synthetic fibers such as Dacron, Orlon, rayon or nylon, or metal fibers such as steel wire. Depending on the nature of the fabric and its ultimate use, mixtures or blends of the above fibers can also be employed. When the invention is utilized as a papermakers felt, Wool fibers, synthetic fibers, or blends thereof, are commonly used.

The fabric or felt I can be woven in endless form or, alternately, a straight length of felt can be hand-spliced by conventional techniques to provide the endless form.

Following splicing, of if the felt is woven in endless form, the felt is cocked or skewed, resulting in the cross yarns 3 being moved to an acute angle with respect to the warp yarns 2, as shown in FIG. 2, and correspondingly bringing the warp yarns 2 closer together with the effect that the overall width of the felt is decreased, with the overall reduction in width depending on the angularity of cocking. The manner of cocking the felt is not critical to the invention and any method can be employed which will adjust the angularity of the cross yarns with respect to the warp yarns at the desired range. The felt can be cocked either manually or by positioning the felt over a pair of spaced stretch rolls such as that disclosed in Patent 3,030,690.

The cross yarns 3 can be skewed to an angle up to 80 with respect to a line normal to the warp yarns 2, and generally the cross yarns are skewed to an angle of 10 to 80, with an angle of about 30 to 60 being preferred. In the uncocked state as shown in FIG. 1, the openings or spaces between the strands 2 and 3 are generally rectangular in shape, while after cocking, the openings between the strands have an elongated parallelogram shape.

After cocking, the felt is stabilized according to conventional procedures. During stabilization, the cocked felt is subjected to one or more physical and/or chemical treatments which reduce the tendency of the felt to return to its uncocked orientation. Various methods may be used to stabilize the felt, and the procedures to be employed are generally determined by the composition of the felt and the utilimate use of the felt in the papermaking process. Stabilization, for example, can be achieved by needling, heat setting, chemical setting or by heat and moisture fulling.

In needling, batts of fibers may be ncedlcrl to one or both surfaces of the woven and cocked felt, and Patent 3,230,599 discloses an apparatus which can be employed in needling the felt for stabilization.

If the felt consists predominantly of synthetic fibers it may be stabilized by heat setting by the application of heat to the woven and cocked felt or by the application of heat and pressure. Suitable methods for heat stabilization of predominantly synthetic fiber felt are disclosed in Patent 3,075,274. If the felt contains synthetic fibers which are shrinkable, stabilization of the cocked felt can be carried out in a chemical bath such 'as that disclosed in Patent 3,094,763.

Wool, or predominantly wool felts can be stabilized using conventional wool fulling procedures whereby heat, moisture and pressure cause the felt to shrink and the fibers to co-mingle. As the cocking of the felt tends to bring the warp yarns closer together and thereby reduce the openness of the felt structure, the cocking can serve as a substitute for a portion of the customary stabilization. In any case, the stabilization is carried out only to a degree which, after stabilization, will still permit free angular adjustment of the cross yarns 3 with respect to the warp yarns 2.

The cooked and stabilized papermakers felt can be installed on a press of a typical papcrmaking machine as shown in FIG. 3. The endless felt 1 is supported for movement on a series of rolls 4, 5, 6, 7, 8, and 9. After the felt 1 leaves the roll 9, a wet Web of newly formed paper 10 is transferred from the Fourdrinier wire, not shown, to the upper surface of the felt and the felt and wet web of paper 10 pass between a pair of press rolls 11 and 12 where the roll pressure serves to extract water from the paper web. The partially dried paper sheet is then transferred from the felt 1 to a second felt, not shown, which carries the partially dried paper web to further drying means.

As previously described, the cocked and stabilized felt is installed in the papermaking machine in a cocked condition in which the cross yarns 3 are located at an angle up to and in most cases at an angle of 20 to 70, with respect to a line normal to the warp yarns 2. As shown in FIGS. 4, 6 and 8, a conventional marker or guide line 13 is applied to the felt and extends normal to the side edges of the felt and the angle of the cross yarns is indicated in FIGS. 4, 6 and 8 by the phantom line AA.

One of the important features of the invention is the ability of the cross yarns to be adjusted in angularity while on the paperrnaking machine and thereby correspondingly vary the porosity and drainage rate of the felt and finish characteristics of the paper. To provide for an adjustment of angularity of the cross yarns 3 of the felt 1, the ends of the shaft 14 of one of the rolls 6 are journalled within bearing blocks 15 which are pivotally connected to nuts 16, and jack screws 17 are threaded with nuts 16. By rotation of the jack screws 17, the axis of the roll 6 can be varied in angularity. For example, by selective operation of the jack screws 17, one end of the roll shaft 14 will be advanced while the other end of the shaft 14 will be retracted. This angular adjustment of roll 6, shown exaggerated for purposes of illustration in FIGS. 6 and 8, has the effect of causing warp yarns to travel successivel greater distances in each revolution of endless travel of the felt with a resultant reorientation of the cross yarns 3 relative to the warp yarns 2. When the desired degree of angularity adjustment has been achieved, the adjustable roll 6 is returned to its original position as shown in FIG. 4, and the new angularity of the cross yarns is maintained until further adjustment.

In the manufacture of paper using felts of conventional construction, the adjustable roll 6 is used to maintain the orientation of the cross yarns along a line normal to the edge of the felt. In the design of conventional felts, a major criterion is that the felt be operated with the cross yarns at a right angle to the longitudinal yarns. If the felt is allowed to skew or bow while operating on the paper machine, the designed operating characteristic are adversely affected. Thus, the adjustable roll 6 is provided on all standard paper machines to keep the felt in it designed configuration. The standard adjustable roll 6, however, is suitable for use as the adjusting means of this invention.

As a manner of illustration, FIG. 4 shows a felt as installed on a press section of the papermaking machine with the guideline 13 being normal to the side edges of the felt and the cross yarns 3 being at an angle of 45 with respect to a line normal to the warp yarns. By adjusting the roll 6 to the position shown in FIG. 6, the cross yarns will be moved to a position, as inicated by the phantom lines A-A, normal to the warp yarns, and in this position the felt will have its most open structure. Adjusting the angularity of the cross yarns from the position of FIG. 4 to the position of FIG. 6 will correspondingly move the warp yarns farther apart and increase the overall width of the felt.

By adjusting the roll 6 to the position shown in FIG. 8, the openness of the felt is decreased and the cross yarns are moved to an angle of approximately 60 with respect to a line normal to the warp yarn. Adjusting the cross yarns to the angularity of FIG. 8 will correspondingly move the warp yarns closer together to reduce the width of the felt and will tend to further elongate the openings between the yarns 2 and 3.

As the angle of cocking increases, the area of the openings between the strands is decreased, but the longitudinal dimension of the openings is increased. The elongated configuration of the openings tends to improve the drainage both forwardly and rearwardly from the nip line, and thus, even though the area of the openings is decreased as the angle of cocking is increased, the drainage rate of the felt is not necessarily reduced due to the improved elongated configuration of the openings.

As the angle of cocking is increased, the longitudinal yarns are drawn closer together, resulting in an improved level of finish in the paper sheet. Conversely, as the angle of cocking is decreased, the longitudinal yarns are caused to separate, resulting in a decrease in the smoothness or finish of the paper sheet.

One of the principal advantages of the papermakers felt of the invention is that by adjusting the angularity when the felt is on the papermaknig machine and while the machine is running, the openin s between the warp yarns 2 and the cross yarns 3 can be increased in size. The increase in size of the openings, as well as the physical manipulation of the fibers relative to each other, serves to dislodge foreign material from the openings and thereby substantially increases the service life of the felt before it i necessary to remove the felt from the machine for cleaning and reconditioning. To provide this cleaning effect, the felt is generally adjusted through an angle of at least 10 and preferably through an angle of about 10 to 45. After the adjustment ismade to increase the openness of the felt structure, the felt can be re-adjusted while on the machine to return the cross yarns to their original angular disposition so that the finish characteristics of the paper being produced will not be altered.

For example, if the papermakers felt is running normally with the cross yarns located at an angle of 45 with respect to a line normal to the warp yarns, as shown in FIG. 4, the felt can be cleaned while on the machine by adjusting the angularity to the position shown in FIG. 6 in which the cross yarns are disposed normal to the warp yarns. As shown in FIG. 7, the area of the openings between the warp yarns 2 and the cross yarns 3 is increased as the felt is adjusted in angularity to the position shown in FIG. 6. The increase in area of the ope-nings, as well as the physical adjustment of the yarns serves to dislodge the foreign material from the openings. After the felt has been adjusted to the position shown in FIG. 6, it is usually returned to its original position, as shown in FIG. 4, so that the finish characteristics of the paper being produced will not be altered.

In some cases, instead of returning the felt from the open position, shown in FIG. 6, to the original position of FIG. 4, the felt is skewed to the position shown in FIG. 10 in which the cross yarns are again at an angle of 45 with respect to a line normal to the warp yarns but are located at an angle of with respect to their original position, as shown in FIG. 4. Adjusting the angularity of the cross yarns from a +45 through the open 90 position shown in FIG. 6, to a 45 orientation will, because of the substantial manipulation or shifting of the yarns, result in a thorough cleaning of the fiber structure. Yet, the cross yarns will have the same angular relationship to the warp yarns after adjustment, as shown in FIG. 10, as in the original structure shown in FIG. 4 and thus the finish characteristics of the paper will not be altered.

As a further advantage, it is possible to adjust the angularity of the cross yarns only along a portion of the width of the felt. If the papermakers felt is normally running, as shown in FIG. 12, with the cross yarns having an angularity illustrated by the line B and the numeral 13 indicating the guide marker, a portion of the width of the felt can be shifted to increase the openness of the felt structure along that portion of the width, as shown in FIG. 13. To adjust the angularity of the cross yarns only along a portion of the width of the felt, a portion of the length of one of the guide rollers is strung so that the portion of the width of the felt passing over the area of the stringing will travel a greater distance. Thus, the cross yarns in the area of stringing, indicated by the line C-C in FIG. 13, will be adjusted or skewed in angularity and the openness of the felt structure in the area C-C will be increased. In place of stringing, other methods, such as the use of adjustable bowed rolls, can be employed to increase the distance of travel of a portion of the width of the felt and thereby provide the adjustment of angularity.

While the drawings illustrate the edge area CC of the felt being adjusted in angularity with respect to the remainder of the width of the felt, it is contemplated that any portion or portions of the width of the felt can be adjusted in angularity in a similar manner. This feature enables certain sections of the width of the felt to be opened for cleaning purposes while the felt is running on the machine, and this feature serves to increase the overall service life of the felt as well as reducing the down time of the papermaking machine.

Although the foregoing description has been directed toward woven fabrics containing cross yarns as the predominant cross-machine members, it should be understood that the principle involved in the invention applies equally as well to fabrics in which cross-machine fibers, rather than distinct yarns, are the predominant and controlling cross-machine members. It is contemplated, for example, that the cross-machine members of the felt shown in FIG. 12 could comprise predominantly discontinuous fibers oriented substantially parallel to the line B. Thus, the term cross fibers as used in the claims is intended to include fibers in the form of yarns as well as dis-continuous fibers oriented in the cross-machine direction, such as produced by needling cross yarns to a degree so that the continuity or integrity of the cross yarns is at least partially destroyed but the fibers remain in a predominantly cross-machine direction.

The benefits resulting from the adjustability of fabrics of this inveutionadjustable drainage, adjustable paper finish, ease of fabric cleaning, and increased service life-are particularly applicable to papermakers felts containing longitudinal yarns and either cross-machine yarns or cross-machine oriented fibers.

In the case of papermakers felts in which the predominant cross-machine members comprise yarns, further benefits result from the angularity of the cross-machine yarns with respect to the longitudinal yarns. For example, in the nip of a papermachine press, the passage of water from the paper sheet through the felt is necessarily through the felt and backward from the pressure point at the nip of the pressure rolls, for felts of conventional construction. With the felt of the invention, the cross yarns are located at an acute angle with respect to the warp yarns, so that at any given time a series of cross yarns, rather than a single cross yarn, will be located under the nip. Thus, there will always be a series of openings or water passageways under the nip at any given time, and this characteristic of the felt, although still favoring the backward drainage vector, also provides forward drainage and results in improved overall drainage characteristics for the felt.

'Further, as the cross yarns are located at an acute angle with respect to the warp yarns, a series of cross yarns will, at any given time, engage the pressure members or cross-machine devices, and this substantially reduces the abrasion of the cross yarns as compared to the normal papermaker felt in which each individual cross yarn strikes broadside against the pressure member.

The angular disposition of the cross yarns has a further advantage in that it guarantees a greater maximum finish level than is possible with the conventional papermakers felt. Spun yarn varies in diameter along its length, and from bobbin-to-bobbin there is a significant variation in diameter. These variations in diameter are transferred to the paper sheet at the pressure point of the nip. When the nip presses against the cross or filling yarns, which are substantially in the same line as the nip in the conventional papermakers felt, an absolute transfer to the paper sheet of the varying yarn diameters is obtained. With the diagonal disposition of the cross yarns in the papermakers felt of the invention, a series of. cross yarns are under the nip line at any given instant, and this tends to average out the inherent variations in diameter in the yarn and promotes improved finish in the paper sheet.

Further, the diagonal disposition of the cross yarns provides openings between the yarns which have a parallelogram shape rather than the rectangular shape found in felts of conventional construction. These parallelogramshaped openings are elongated in the longitudinal direction, providing for flow of expressed water in the longitudinal direction through the felt, and as a result minimizing potentially-destructive longitudinal fiow of water through the newly formed paper web. Accordingly, greater nip pressures and higher operating speeds than those possible with felts of conventional construction can be utilized.

The papermakers felt of the invention may be woven in a relatively open mesh construction, and after weaving is cocked or skewed to provide the desired angularity of the cross yarns. By being able to weave the fabric with a relatively open mesh construction, a substantial increase in productivity of weaving equipment is obtained.

At the same time, the open structure greatly facilitates the hand splicing operation which is necessary to produce felts which are too long to be constructed in an endless form. Splicing, as is well known in the art, must be of a nature so that the water removing properties of the felt are not materially changed in the area of the splice. The felt of the invention can be woven with a more loose construction than the conventional felt due to the fact that the cross yarns are subsequently cocked which brings the warp yarns closer together and reduces the overall width of the felt. By weaving with a loose construction, both the manual dexterity and physical force required to splice the ends of the felt are reduced, and the loose woven construction also permits greater control of the tension applied to individual yarns during the splicing operation, for the yarns are relatively free from the restricting contact of adjacent yarns.

The skewed or cocked arrangement of the cross yarns also spreads the spliced area of the felt, if the felt is not woven in endless form, over a diagonal line, thereby preventing the entire splice from passing simultaneously under the nip and reducing the possibility of variations in drainage rate, variations of finish level, or press roll bounce.

The magnitude of the effect of cross yarn angularity on distribution of the influence of cross yarn properties is best illustrated by the following table. This table shows the approximate number of cross yarns or picks which would pass through the nip line, that is, the theoretical line of contact between two non-deformable cylinders, of a set of pressure rolls in a paper machine using a felt having an operating width of 200 inches, when woven with 10, 20, 30 and 40 picks per inch, respectively, and when skewed at 0, 30, 45 and 60.

TABLE-EFFECTIVE FELT VVIDTH200 INCHES Picks/ inch as woven Picks under nip line in the loom: 0 skew Picks/ inch as woven Picks under nip line in the loom: 30 skew Picks/ inch as woven Picks under nip line in the loom: 45 skew Picks/ inch as woven Picks under nip line in the loom: 60 skew Because of inherent felt and paper compressibility as well as the generally deformable materials used as covering for papermachine press rolls, a nip in actual practice is defined as an area rather than as a line of contact. The distance, in the longitudinal direction of the felt, over which the nip operates is of the order of magnitude of one inch. Thus, in actual practice, more than a single cross yarn will be within the nip at any given instant, using a felt of conventional construction. Within the present feltmaking art, it is possible to weave a felt of conventional construction having as many as cross yarns/inch, where smoothness and finish are required. Although such a felt would have 140 picks within a one-inch nip zone, this figure is at least one order of magnitude smaller than the picks under the nip possible with a felt of this invention woven with few picks in the loom. In addition, for felts of equivalent finish level in the paper, the felt of this invention would exhibit superior drainage characteristics.

To provide the advantages of the invention, the warp yarns 2 and cross yarns or fibers 3 need not be woven or interlaced. Instead, the cross yarns or fibers can be mechanically interlocked or needled to the warp yarns as long as there is free adjustability or angular mobility of the cross-machine members of the fabric with respect to the longitudinal members.

While the above description was directed particularly to the use of the adjustable fabric as a papermakers felt, it is contemplated that the invention can be used in any application for filtering fluids where it is desirable to adjust the porosity of the filtering fabric. For example, the invention could be applied to a Fourdrinier wire for a papermaking machine, a forming fabric, a drying fabric, a drying oven conveyor, ,or any other type of filtering device involving the passage of a fluid through a porous moving web.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. An apparatus of the class described, comprising a Web formed of a series of generally parallel first strands and a series of second strands disposed at an acute angle up to 80 with respect to a line normal to said first strands and defining a plurality of openings therebetween, said second strands being freely adjustable with respect to said first strands whereby the angularity of said second strands can be selectively varied to vary the effective size of said openings and change the porosity characteristics of said web, support means for supporting said web, and adjusting means for adjusting the angularity of said second strands with respect to said first strands when the web is supported on said supporting means.

2. The filtering apparatus of claim 1, in which said apparatus is a papermakers felt.

3. The filtering apparatus of claim 1, in which said first and second strands define a plurality of elongated parallelogram shaped openings in said Web.

4. An apparatus for filtering fluids, comprising an endless web, web supporting means for supporting the web in endless travel, said Web including a series of generally parallel spaced first strands disposed longitudinally of the direction of travel of the Web and including a plurality of cross fibers disposed at an acute angle up to 80 with respect to a line normal to said first strands and being freely adjustable in angularity with respect to said first strands, and adjusting means for adjusting the angularity of said cross fibers with respect to said first strands when the Web is supported for endless travel.

5. The apparatus of claim 4, in which said web supponting means includes a series of rolls to support the web in endless travel, and said adjusting means is operably connected to one of said rolls.

6. The apparatus of claim 4, wherein said acute angle is in the range of 30 to 60. 7

7. The apparatus of claim 4, and including a pressure member disposed to engage'said web along a nip line extending normal to said first strands, said second strands being disposed diagonally to said nip line.

8. A fabric web for use on a paperrnaking machine, comprising a series of generally parallel warp yarns, and a plurality of generally parallel cross fibers interwoven with said warp yarns and being freely adjustable in angularity with respect to said warp yarns, said warp yarns and cross fibers defining a plurality of openings therebetween, said cross fibers being located at an angle up to with respect to a line normal to said warp yarns, and adjusting means for adjusting the angularity of the cross yarns with respect to the warp yarns through an angle of at least 10 when said web is installed on said machine to thereby vary the effective size of said openings and vary the porosity of the web and the finish characteristics of the paper.

9. In a method of papermaking, the steps of mounting an endless web on a papermaking machine, said web having a series of generally parallel spaced warp strands extending in the direction of travel of said web on said machine and having cross fibers extending across said strands and d-e fining a plurality of openings therebe-tween, said cross fibers being freely adjustable in angularity with respect to said warp strands and said cross fibers being disposed at an acute angle up to 80 with respect to a line normal to said warp strands, and adjusting the angularity of said cross fibers with respect to said strands through an angle of at least 10 while the web is on the machine to vary the size of said openings and change the porosity of said web.

10. The method of claim 9, wherein the cross fibers are disposed at an angle smaller than said acute angle after said adjusting, and including the step of readjusting the angularity of said cross fibers to substantially return the porosity of the web to its original condition.

References Cited UNITED STATES PATENTS 2,401,990 6/1946 Van Orman l6 l 3,086,276 4/1963 'Bartz et al 2872.2

FOREIGN PATENTS 23,984 1896 Great Britain.

SAM IH N. ZAHARNA, Primary Examiner. 

